Intraoperative Computed Tomography and Nexframe-Guided Placement of Bilateral Hippocampal-Based Responsive Neurostimulation: Technical Note

Introduction Surgical resection of a lesion that correlates with seizure onset in patients with epilepsy can dramatically improve seizure burden and quality of life. For bilateral hippocampal lesions, bilateral resection comes with a risk of severe cognitive deficits. Responsive neurostimulation (RNS) devices offer a new modality to treat multifocal lesions in a reversible manner including bilateral hippocampal stimulation. We describe technical aspects of Nexframe-assisted placement of bilateral NeuroPace mesial temporal electrodes and case examples. Methods Retrospective chart review was performed for 4 patients who underwent bilateral mesial temporal RNS placement for medically intractable epilepsy. Operative techniques were assessed and modified. Ambulatory electrocorticographic recordings and a subanalysis of available data are summarized. Results Eight electrodes were placed in 4 patients, who were followed for up to 6 months. One out of 8 electrodes was revised due to vector error >3 mm; after surgical technique modification, all subsequent electrodes were reliably placed in a single pass with <2-mm vector error. Using patients’ seizure diaries, seizure semiologies were correlated with ambulatory ECoG recording patterns and subanalyzed; 51.4% were left sided, 15% were right sided, and 33.6% were indeterminate. Conclusions We report herein the technical nuances of adapting Nexframe to hippocampal-based depth electrode RNS system placement. Our group has extensive experience with Nexframe for accurate and safe deep brain stimulation electrode placement. Our preliminary data with bitemporal RNS placement suggest similar accuracy and safety.